Manufacture of alumina particles



Jan. 26, 1954 v. HAr-:NsEL

MANUFACTURE OF ALUMINA PARTICLES Filed Aug. 5o, 1951 HEATED AIR A1C15 SOLUTION -|NVENTORI VLADIMIR HAENSELy BY 6M AT TORNEYSI Patented Jan. 26', 1954 2,667 ,404 MANFACTURE OF ALUMINA PARTICLES Vladimir Haensel, Hinsdale, Ill., assigner to Universal Oil Products Company, Chicago, Ill., a

corporation of Delaware Application August 30, 1951, Serial N o. 244,450

(Cl. ,Z3-143) 3 Claims.

This invention relates to the manufacture of aluminum hydroxide and more particularly to a novel process for precipitating alumina from a solution of a chloride of aluminum.

In accordance with the present invention a solution of a chloride of aluminum is directed through a pipe line or other suitable conduit into a spray drier, and ammonia is commingled with said solution in the pipe line. As will be hereinafter set forth, this method offers' numerous advantages over the prior art methods which are briefly described in the following paragraph.

In one method of the prior art, ammonium hydroxide is commingled with an aluminum'chloride solution in a'vat or mixing tank and aluminum hydroxide is precipitated therein. The resultant slurry may be pumped to a spray drie'r for effecting evaporation of water and drying of the resultant aluminum hydroxide. This method has the disadvantage that the precipitated aluminum hydroxide results in a viscous mass which is difhcult to pump into and through the spray nozzles and thus requires considerable dilution of the mass in order that it may be pumped satisfactorily.

Another method of prior art comprises spraying an aluminum chloride solution into an atmosphere of ammonia. This method has the disadvantage that the ammonia concentration is difficult to regulate and results in particles which are not uniform. Furthermore, this method has the additional disadvantage that an excess of ammonia is utilized and this in turn means either that ammonia is lost from the System or requires additional equipment to recirculate the same.

It will be noted that the novel process of the present invention avoids the objections of the prior art methods. By injecting the ammonia into the aluminum chloride solution on its way to the spray drier, more concentrated slurries or solutions of aluminum chloride may be used because these will not contain precipitated aluminum hydroxide. Furthermore, the aluminum hydroxide in the novel process of the present invention is not allowed to remain in the wet stage for a considerable time before spray drying as is otherwise encountered in the prior art method where the ammonia is added to the aluminum chloride solution in a mixing vessel. Another advantage to the process of the present invention is that it is unnecessary to store large volumes of slurry in the event that the spray drying equipment should not be in working condition, and thus the precipitated aluminum hydroxide will not be subjected to still longer periods of wet aging prior to the spray drying thereof.

The novel features of the present invention are described further in the accompanying diagrammatic flow drawing whichillustrates one speciiic embodiment in which the invention may be practiced.

Any suitable chloride of aluminum may be used in accordance with the present invention and conveniently comprises the commercially available aluminum chloride hexahydrate. Other suitable but not necessarily equivalent chlorides of aluminum include those containing a'chlorine to aluminum mol ratio lower than 1:3 as contained in AlCls. Such chlorides of aluminum may be prepared, for example, by digesting aluminum chloride solutions withaluminum metal to form a chloride of aluminum containing a lower chlorine content, or by any other suitable method. Y

As hereinbefore set forth, the aluminum chloride solution may contain ka higher concentration of aluminum chloride than utilized in the prior art method previously described. This solution is directed from any suitable source through line l to spray drier 2. Gaseous ammonia or an ammonium hydroxide solution is directed through 4line 3 into line I to commingle with the aluminum chloride solution on its Way to the spray drier. It is understood that any suitable means may be employed for commingling the ammonia With the aluminum chloride solution as, for example, an elbow or turned pipe facing in the direction of iiow, said elbow being oi smaller diameter than the diameter of the pipe line carrying the aluminum chloride solution, a vapor nozzle, etc. In order to avoid excessive precipi tation of aluminum hydroxide in this-line, it is preferred that the ammonia is commingled with the aluminum chloride just prior to introduction of the mixture into the spray drier. The exact point of introduction may Vary with the particular plant equipment. However, it is preferred that after the ammonia is introduced, the mixture be introduced into the spray drier within about 10 minutes and preferably not in an excess of about 5 minutes. In a preferred operation the ammonia shouldrbe injected just prior to introduction of the mixture into the spray drier.

In the case here illustrated the mixture of aluminum chloride and ammonia is directed through .employed within the scope of the present invention. In the case here illustrated, heated air is introduced through line 5i to the vupper portion of the, spray drier 2. It is understood that in place of air any other suitable heating medium may be used including hydrogen, nitrogen, fuel gas, etc., which had been' heated. to the desired temperature. and also that the` heating'. medium may be introduced inte the sidel ortbottom off the spray drier.

In the case here illustrated, the dried particles of alumina are removed from the lower portion of the spray drier through line; zcontai-ning valve l. In another embodiment,A one or more cyclone separators may be disposed' wit-hinA or adjacentA to the spray drier to separate the alumina particles from heated air, and each is separately Withdrawn from the cyclone separator. i'sVV understood that, when desired, a layer of: Water, oil or other suitable liquid1may be disposed in the lower portion of the spray drier. andutilized as a means of collecting and'r removing' the alumina. particles. from the spray drying zone. One method, not illustrated, comprises the use of a flowing stream of water at the bottom of thespray drier to collect and withdraw the' alumina particles.

The temperature employed.` in the sprayV drier should beY sufficient to effect the desired evaporation of Water and drying ofthe aluminum hydroxide. In the case here illustrated in the' drawing, satisfactory drying has been obtained when utilizing heated air introduced atv a temperature of from about/500 to about 800 F1, al'- though lower or higher temperatures. may be employed, which may range from 400" F. or lower to 1000 F.. or higher.

The particles withdrawnfrom the. spray drier are referred in the present specification and claims as alumina. However. it is understood that these particles may comprise aluminum oxychloride or other combinations of aluminum, oxygen and chlorine. The exact composition of' particles will depend upon the particular temperature employed in the spray drier and in some cases may comprise aluminum hydroxide. However, these particles may be subjected to a subsequent drying and/ or calcining treatment which will serve to produce a nal product comprising, predominantly alumina.

The alumina particles withdrawn from spray drier 2 generally will be of substantially spherical shape, and the size ofthe particles will depend` upon the size of the spray nozzle or the speed of rotation of the rotating disk. The substantially spherical particles are of advantage for use as-refining agents, dessicating agents, dehydrating agents, etc.,.as well as forY use asa carriensupport, or. a component of' a catalyst for the conversion of. organic compounds. The spherical particles withdrawnv from the spray drier, when desired, may be subjected to anyl suitable purication treatment to remove componentswhich are impurities in the process for which the alumina particles are subsequently to be used. These purication steps-generally include washing with water. or other solutions to remove soluble impurities. After washing, the alumina. particles may be dried-at a temperature of. from about 200 to. about 600 F. for a period of fromabout 2. to 24 hours or more andl then` calcined at a. temperature offromabout 700' to about1200 F. or morefor a period'of from about 2 to 12 hours or more. In somecases the Washed alumina particles may be compositedwithH the other catalytic components before the drying and/or calcining treatments. In another em.- bodimentmparticularly` when the alumina: particles are recoveredasapowder, the powdermay be commingled: with a suitable lubricant and then pilled, extruded: or otherwise formed' into. larger@ particless of'. uniform size andshape;

The. alumina, as prepared; in the above manner, is particularly suitable-` for use irf the manufacture of active catalysts for the conversion of organic compounds. composited in any suitable manner with a noble -metal or compound thereof, and particularly platinum. orA palladium, in the manufacture of catalysts for use. in the reforming of low antiknock gasoline fractions, dehydrogenation reactions, etc. The alumina lis also particularly desirable-for compositing with metals, oxides or other compounds of the elements in the left hand columns of groups 4, 5 and/or 6 of the periodic table to prepare dehydrogenation catalysts. It is' understood' that these are merely illustrative uses to which the alumina maybe applied` and that other'uses of the alumina areincluded within the broad scope of' the present invention'.

'IheV following example is introduced to' illustrate further the novelty and* utility' of the present invention but notv with the'intention of unduly limiting the same;

A solution` of aluminum chloride hexahydrate in water may be prepared to contain aboutA 35% by weight of Al'Cls. This solution. may' be directed through line l to sprayidrier'; Gaseous ammonia maybe introduced through linel 3 and commingl'ed with the aluminum chloride solution, theY mixture being passed to the spray drier within one minute from thev time of mixing. Thev mixture is sprayed in the drier by' means, of ai rotating disk, the drier being heated'layV means' of heated air introduced at 600' F; through the top of the drier; 'I'he heated air and alumina particles. are separated in a cyclone. separator, and the spray dried particles'are removed fromY the sprayY drier and then washed with water" 1. A process for the production ofA alumina particles from a solution of a chlorideo aluminum which comprises supplying a stream of said solution to a drying zone', introducing ammonia' into said stream while in transit to said zone, promptly thereafter sprayingv the resultant mixture into the drying zone and therein contact'- ing the sprayed'mixture with a gasat a temperature suici'ent to evaporate waterfrom the mix-r ture.

2. The process of. cl'aiin 1` further characterized' in that said mixture is sprayed'` into the drying' zone within10 minutes from the time said' ammonta is oommingled with said solution.

3. The process of claim 1' further'characterized in, that saidammonia is injected asgaseous am'- monia into said solution.

VLADIMIRv I-IAEN SEL.

References Cited in the'le of' this patent UNITED STATES PATENTS Number Name Date 1,300,110l Betts" .Apr. 8, 1919.` 1,337,191 Buchner Apr; 20; 1920 1,337,192 Buchner Apr. 20, 1920` 2,036,508 Svendsen Apr. 7, 1936 2,333,943 Muskat Nov. 9; 1943 OTHER RElElftENCES'v Comprehensive Treatise on Inorganic and Theoretical Chemistry; page: 319.; Mellor,l vol. 5. Longmans, Green and Co. Copyright:1024..V

Thus the alumina may be 

1. A PROCESS FOR THE PRODUCTION OF ALUMINA PARTICLES FROM A SOLUTION OF A CHLORIDE OF ALUMINUM WHICH COMPRISES SUPPLYING A STREAM OF SAID SOLUTION TO A DRYING ZONE, INTRODUCING AMMONIA INTO SAID STREAM WHILE IN TRANSIT TO SAID ZONE, PROMPTLY THEREAFTER SPRAYING THE RESULTANT MIX- 